The entire disclosure of the copending U.S. patent application Ser. No. 09/347,894 entitled DISTRIBUTED MANAGEMENT OF AN EXTENDED NETWORK CONTAINING SHORT-RANGE WIRELESS LINKS, filed on even date herewith, the specification of which is hereby incorporated by reference.
The present invention generally pertains to communication systems, and more particularly to an inter-networked communication system containing a dual-powered node.
Traditionally, electronic devices used in an office network relied on alternating current xe2x80x9cACxe2x80x9d power as their power source. A typical office configuration consisted of, at a minimum, several computers, a printer, and a central data storage device. The traditional office also typically employed hardwired connections from one device to another. Conveying information from one device to another was accomplished by using a wired backbone network. Thus, a user desiring to route data from a computer to a printer sent the necessary data over a cable from his or her computer to a local printer.
More recently, office configurations incorporate both AC powered devices and battery operated, or wireless, devices such as personal digital assistants (xe2x80x9cPDAxe2x80x9d), pagers, laptop computers, and the like. While these devices run on battery power and thus do not require a wired connection for power, unless they are configured with a transmit antenna and an amplifier and are located in close proximity to a device capable of receiving data transmission, these wireless devices must transfer data to external devices via traditional wired backbones. Technologically speaking, it is fairly straightforward to couple a wireless device to a transmit antenna and an amplifier for the purpose of routing data from the wireless device to a standard AC device. One difficulty with this configuration is that wireless devices, unlike AC devices, have a limited power supply and, therefore, must minimize power consumption. System designers thus generally must make a trade-off between extended transmission range and power conservation.
Transmission range of a wireless device without an amplifier is typically limited to somewhere on the order of ten meters. If the user is operating the wireless system exclusively in his or her office, this range limitation is typically not an issue. If, however, the user seeks to operate the wireless device outside of his or her office, AC devices intended to receive the data within the office will be out of range. Even if there are other AC devices within range of the wireless unit at the moment that the user wishes to transmit data, these intermediary devices will be unhelpful unless some wired backbone is in place to transfer the data to the desired AC device. That is, the data will remain stored at the AC device receiving the data. For example, assume a user is in conference room and is using a PDA out of range of the AC devices in his individual office. If the user wishes to print a color copy of a chart stored on the PDA using the color copier located in his office, he will be required to leave the conference room and move within the range of his color printer. This undesirable limitation has been overcome by employing a wired network connecting all of the AC devices in a particular office. Once the devices are physically connected, it becomes possible to route data from the wireless device to anywhere in the office. Unfortunately, such hardwired networks are inflexible and can be difficult to install and maintain.
Briefly, therefore, this invention provides for a method and apparatus for internetworked communication. The system of the invention includes at least a first wireless network containing a first plurality of wireless nodes and an overlay network containing a second plurality or wireless nodes. In a preferred embodiment, a first dual-power node participates in both the first wireless network and in the overlay network and operates in a time-division multiplexed manner. Specifically, the first dual-power node communicates with the first plurality of wireless nodes at a first power level during certain time slots, and with at least one of the second plurality of wireless nodes at a second power level during other time slots. The inventive system may also include a third wireless network containing a third plurality of wireless nodes, at least one of which is also included in the second plurality of wireless nodes.
In a preferred embodiment, the dual-power node contains a low-power transceiver, a high-power transceiver, and a controller for facilitating toggling between operation in high-power and low-power nodes. The overlay network may also contain a second dual-power node capable of communicating with the first dual-power node at high power and with the third plurality of wireless nodes at a lower power.
The overlay network is preferably initialized pursuant to a protocol in which one high-power device becomes operative as a master node and the remaining high-power devices act as slave nodes. Pursuant to this protocol, the master node transmits a notification signal identifying itself as a high-power device and indicating the identity and connectivity of its overlay network. This notification message signals the other high-power devices that the overlay network contains a master node and that additional nodes seeking to join the network should act as slave nodes. Accordingly, when a high-power node or a dual-power node initially powers-up, it monitors the network to determine whether any of the high-power or dual-power devices are presently acting as master nodes. If a master node does not currently exist, the high-power or dual-power device assumes the role of master node.